1. Field of the Invention
The present invention relates to an image forming device for forming in the air an image of pictures or characters drawn or displayed on a surface, and also relates to a touch-less display switch which utilizes such an image forming device.
2. Description of the Prior Art
Conventionally, static or animated pictures or characters displayed on a picture plane of a display device are adapted to be observed by an observer while he visually recognizes the picture plane itself through a surface structure of the display device.
However, such pictures or characters are those merely displayed on the picture plane, and they lack amusingness.
In addition, various kinds of display switches called "touch-panel switches" have been proposed. In general, such switches are disposed on an upper surface of a display device and have a common basic construction which includes a contactor or a specific member having a variable impedance covered by a transparent sheet. The contactor is normally made of a transparent electrode.
Here, the term "touch-panel switch" means a multi-function switch (operable as an input/output terminal as well as a switch) which is operable to open and close its contact when an operator touches or pushes a transparent sheet (or a contact) of the switch with his finger(s), or when the finger(s) of the operator is moved away from the transparent sheet after contacting the same.
Since, with the conventional touch-panel switch, the operator has to touch the transparent sheet of the switch after he visually recognizes keys which are displayed on a picture surface of the display device and which are positioned at the back of the transparent sheet, there has been a serious drawback that the transparent sheet tends to be stained in addition to the drawbacks of lack in amusingness of the display device itself.
Further, for the reason of stains, the conventional touch-panel switch is not suitable for use as an input/output terminal for an instrument or an apparatus in which particular consideration should be given to sanitary aspect.
For example, as for an operation switch for a medical instrument, it is often desirable that the switch is turned on and off while the operator does not touch the switch. As is well known, in recent years, nosocomial infection by virus has been caused a serious problem. Thus, the conventional touch-panel switch is not appropriate to be used where it is not suitable for uses where the operator directly touches a switch (or its keys).